1. Field of the Invention
The present invention relates to portable printers and sheet feeders and more particularly to such printers and feeders which are relatively small, light weight and which may be battery powered.
2. Description of the Related Art
A typical printer receives data from a computer for printing text and/or graphic images on print media such as paper. Often, printers have automatic sheet-feeding capability. A stack of paper is inserted into a tray in the printer which thereafter moves the paper, one sheet at a time, past a printing device, such as an ink-jet print cartridge. Generally the printer and paper feeder are integrally formed and have power requirements which make battery power impractical. Printers which are driven by desk-top computers and the like typically must be configured into different operating modes. To do so, information must be provided to the printer concerning different aspects of the printing. For example, there are commonly printer settings for paper size, high-quality versus high-speed (draft) printing, text size, character set selection and other variables which affect the manner in which a document is printed.
Prior art printers utilize DIP switches, keys and/or light emitting diodes to select various configuration options. Such prior art printers are somewhat cryptic in that the user typically needs a manual to interpret the meaning of a particular switch position.
It would be desirable to provide a method and apparatus for configuring a printer which is simple, easy to operate and intuitive. It would also be desirable to provide such a method and apparatus which is relatively inexpensive to implement in a printer design.
In liquid ink printing systems, such as ink jet printers, the ink or other liquid printing solution is wet immediately after the ink is applied to the paper (or other media such as an overhead transparency). The ink must dry before a subsequently printed sheet contacts the printed paper surface in order to avoid smudging the previously applied ink. Known methods of drying the ink include a heated platen. In that arrangement, a flat surface over which the paper glides after it has been printed on is heated. By heat conduction through the paper itself, drying of the ink is hastened so that the ink is sufficiently dried to prevent smudging when a newly printed page comes into contact with it.
Another known method of addressing the wet paper problem is by means of a pair of active wings, as is employed for example in the Hewlett-Packard DESK JET printers. The wings are called "active" because they are moveable, driven by an electro-mechanical assembly. The wings initially hold a newly printed page spaced apart from a previous printed sheet. After printing is complete, the wings move to a second position to allow the printed page to drop onto the previously printed sheet. Therefore, there is a delay equivalent to the time of printing an entire page before the printed page comes into contact with a previously printed page. In general, the object is to provide an adequate delay time before a newly printed page comes into contact with the last previously printed page so that the ink is sufficiently dry.
Known methods of addressing the wet paper path problem are inadequate, especially in the context of a portable ink jet printing system. In a portable ink jet printing system, size, weight and power requirements are critical. Size and weight considerations obviously are important to providing portability. Power requirements must be minimized to allow operation of the printing system using battery power. The heated platen method, in addition to requiring multiple components, draws substantial power from the power source in order to heat the platen. The "active wings," approach also is undesirable because of its complexity and power consumption for powering the electro-mechanical assemblies necessary for actuating the active wings. What is needed is a way to dry ink in a manner that minimizes size, weight and power requirements for use in a portable liquid ink printing system.
It would be desirable to provide a printer which delays depositing a printed sheet on top of a previously printed sheet until after a time elapses sufficient to allow the ink to dry on the previously printed sheet. It would also be desirable to provide such a printer which does not use excessive power and which neatly stacks printed pages as they exit the printer without smudging the newly printed ink.